The rapid climate shifts observed in the glacial climate are analysed. The transitions into the
warm interstadial states, the onsets, are easy identifiable in the record. The distribution of waiting times
between consecutive onsets is well fitted assuming the remaining residence time in each state to be
independent on the past. That implies that it has a simple no memory exponential waiting time
distribution, but with mean waiting time depending on the climate state. The mean waiting time
from one onset to the next is around 2400 y.
The most likely (maximum likelihood) distribution derived solely from the onset sequence is rather insensitive
to the mean waiting time in the warm interstadials in the range 400-1200 y. When extending the
analysis to include the transitions from the warm interstadials to the cold stadials observed with a
larger uncertainty, the distributions in the two states are well fitted to exponential distributions with
mean waiting times of
around 800 y in the warm state and around 1600 y in the cold state. This observation is an important piece in
the climate puzzle, since the fact that the climate is a no memory process indicates that the transitions
are noise induced and the mean residence time in one state indicates how stable that climate state is to
perturbations. The possibility of a hidden periodic driver is also investigated. The existence of such a
driver cannot be ruled out by the relatively sparse data series (containing only 21 onsets). However,
since the record is fitted just as well by the much simpler random model, this should be preferred
from the point of view of simplicity.